Bird research

Museum Calceo-Zarianum 1622

til toppenCollecting and preserving beautiful objects of different origin has been popular throughout the ages. At the time of the great geographical discoveries at the end of the 16th century, a variety of zoological, botanical and geographical items were brought to Europe where they became fashionable collectors pieces for the rich. These collections were given a variety of names such as theatrum naturæ, curiosity chamber, cabinet of natural history specimens, etc The diligent collecting and experimentation of the taxidermists in the past has formed the firm basis on which modern taxidermists work today.

til toppenA taxidermist does not choose his job only because he or she likes to work as an artist – you can earn much more in other exciting jobs – but because of the interest in animals. Both things are important for being a good taxidermist.

til toppenA taxidermist can record a lot of observations while working with dead animals, weights and measurements can be taken and put on a data base, which later, when the material is large enough, can be systematized and published. Other people – even professionals – only seldom have the opportunity to make these observations, and they are important, because they enhance the understanding of many biological relations. (cf. the Reference list).

til toppenTo make these records the exact date of the death of the bird is of the greatest importance, but also information about the place where it was found and the cause of death, if known, are important information


til toppenThe following information is taken from every bird:

  • the scientific name and the registration number
  • sex and age
  • skull oss.
  • date of death
  • time of the day if known
  • the locality (with co-ordinates)
  • the cause of death if known
  • the mass (all weights up to 500g taken with a Sartorius 1608 MP accurate to 1:1.000g)
  • State of condition (normal, little fat, fat, very fat, a little lean, lean, very lean.), mass of furcula fat
  • Colour of iris, bill, inside upper mandible, palate, mouth and tongue, legs and feet, claws, sole and naked skin.
  • length of humerus, two measurements of both left and right humerus (for asymmetrical studies)
  • length of femur, two measurements of both left and right femur (for asymmetrical studies)
  • keel length, two measurements
  • wingspan
  • wing area after: Hedenström, A. & A. P. Møller. 1992: Morphological adaptations to song flight in Passerine birds: A Comparative study. Proc. Biol. Sci. 247 No. 1320: 183-187.
  • wing length, (max) two measurements of both left and right wing (for asymmetrical studies)
  • bill length, length of culmen from tip to geginning of horny covering of bill
  • bill dept from the highest point of bill
  • bil width from the widthest point of bill
  • tail length, two measurements of both left side and right side of the tail (for asymmetrical studies)
  • T6 from left side, total length and mass (e.g. for studies og growth bars)
  • tarsus length, two measurements of both left and right (for asymmetrical studies)
  • length between pubis
  • diameter of iris and eye-ball
  • diameter, width and mass of both lenses and notes if opaque (cataract)
  • mass and measurements of the spleen (immune system)
  • mass and measurements of the bursa Fabricii (immune system)
  • mass of the thymus from left and right side of the neck (immune system)
  • mass and measurement of thyroid of larger birds
  • mass of the brain
  • mass of the liver
  • mass of the heart
  • mass of the gizzard
  • mass of cutica gastrica
  • mass of kidney
  • mass of salt glands
  • mass and description of the food, if found both in crop, proventriculus and gizzard mass given separate and food stored (decaying parts are rarely stored)
  • description of food
  • mass of the lungs, left and right, only if not bloody
  • mass (if larger) and measurements of both testes and their colour
  • mass of both M. pectoralis
  • mass of both M. supracoracoideus
  • testes, length and width of both left and right, mass if larger
  • testes colour
  • measurement of the ovary and mass if large
  • oviducht (straight = never bred, sinuous = have bred), and mass if swollen
  • measurement of the gall bladder
  • measurements of left and right adrenal glands, only larger birds
  • caecum (length of both and the length to anus)
  • length of the intestine and weight with content
  • description of possible fault bars in wings and tail feathers
  • description of possible feather holes in wings and tail feathers
  • description of possible stage of moult, also if black feather follicles are found on skin inside
  • description of all abnormalities and diseases
  • description of discoloured feathers (often hidden on the finished skin)
  • information of recovery of ringed birds

til toppenBesides all these data it is also noted if parasites are found and ectoparasites and grit are kept, using floating techniques for grit, and stored. Endoparasites are stored in spirit. The size and mass of eggs in development and found calies are counted. If feathers are lost under the skinning process they are also stored for stable isotope analyses. For ongoing research other measurements are taken, e.g., how much weight feathers from different parts of the body can carry, uropygial glands size and mass and stored, orange fat deposit, age changes by birds with known age, “horn” length and badge size.Final are DNA probes taken from all skinned birds and the trunk skeleton kept. All infornation are not only written on a label and a catalogue but also put on an Exel database with about 200 columns.

til toppenPlease, take a look also at the Reference list to see the result of current research published thanks these information.

til toppenOf course such a large amount of data give immense possibilities for studies if only the number of each species is large enough and from all months of the year. Some  research examples are presented below:

  • Barn Owl and asymmetry: The northernmost range of the Barn Owl in Europe is Denmark. Asymmetry is a sign of stress in youth. Therefore we study if the percentage of asymmetric birds is higher in Denmark, where the demands for survival are more extreme than in Germany. And is it different from year to year ?
  • Traffic accidents versus birds collisions with windows: Asymmetry in the length of left and right wing and length of left and right side of tail must result in less manoeuvrability. If this hypothesis is right, there must be a greater percentage of traffic casualties than window collisions.
  • The influence of the song on the immune system: It is a fact that singing is hard work. The energy source used for singing must be missing in the fight against e.g. parasites. Therefore we suppose there may be a connection between song and the immune system. Therefore we study the spleen of the species with a large song repertoire. This is also interesting from another point of view because it is known that females prefer males that show staying power in their singing.
    This work is now published, see the Reference list.. (“The evolution of song repertoires and immune defence in birds”)



The European Kingfisher is often killed by window collision.

til toppenAfter 11 years study of the Long-eared Owl it is documented that there is a significantly biased sex ratio towards females during the winter months in western Denmark, while sex ratios approached parity in eastern Denmark, Sweden, central and southern Germany. The sex ratio from other neighbouring contries is also described. None of the present hypothesis for differential migration explain adequately the pattern that the largest – here the female – migrate. An alternative hypothesis is presented. Please read the article: Sex differences in winter distribution of Long-eared Owl in Denmark and neighbouring countries.

til toppenIf you should be interested in reading a popular summary of the scientific result of a study of one thousand House Sparrow skins collected by Johannes Erritzoe please read The Common House Sparrow is actually also fascinating.

From 2000 to 2010 a study of bird traffic casualties was examined, in which four routes, of 1km length each, and one 1.5km long, were checked on foot and bike for dead birds every week; all roads near Taps, Denmark 55.23N 09.28E. The following objectives was pursued.

til toppenIn October 2002 Johannes Erritzoe published an article called “Bird traffic casualties and road quality for breeding birds”. The article is available here

til toppenBesides different research works Johannes Erritzoe has now written a monograph: “Cuckoos of the World” in co-operation with , Dr. Clive Mann, London, Frederik Brammer, Sao Paulo and Dr. Richard Fuller, Queensland. The book is published in the famous Pica Press series June 2012

. Johannes Erritzoe has also in the last years made another book: “A Dictionary for Ornithologists” in co-operation with Kaj Kampp, Copenhagen, prof. Kevin Winker, Alaska, and Dr. Clifford Frith, Queensland, to facilitate the communication between ornithologists all over the world. It is now published by Lynx in Barcelona with the title: The Ornithologist’s Dictionary.

til toppenFor curators it may be of interest to note, that most of Johannes Erritzoe’s research is based on his collection of bird skins and skeletons. How this collection was built up and is managed can be read here

til toppenDuring his many years of research Johannes Erritzoe has encountered many odd rarities from the nature, like e.g. a peacock changing sex after 18 years. Read more here

In April 2009 was the House of Bird Research from the Danish Invironment authority “Skov & Naturstyrelsen”  (now called Naturstyrelsen) acknowledged as a Scientific Institute. See CITES